Through the years, many medical devices have been developed for the purpose of performing procedures wherein it is necessary to somehow cut or incise the tissue of a patient. For specific applications, interventional devices have been developed that are capable of incising tissue at predetermined locations within the vasculature of a patient. In these cases, it is necessary for the device to be maneuvered through the vasculature. Accordingly, a major consideration involves the prevention of an inadvertent or unwanted cutting or incising of tissue as the device is either being advanced into or withdrawn from the vasculature.
An example of an interventional medical device that has been developed for performing certain in situ procedures of the type mentioned above is disclosed in U.S. Pat. No. 5,556,405. This patent issued to Lary for an invention entitled “Universal Dilator with Reciprocal Incisor”, and is assigned to the same assignee as the present invention. As exemplified in this patent, one way to protect against the inadvertent cutting of tissue in the vasculature of a patient is to hold the cutting elements inside a protective housing as it is being moved in the vasculature. Then, while holding the protective housing stationary, an independent mechanism is used to selectively move the cutting elements out of the protective housing so they can be used for cutting. Not all interventional medical devices, however, lend themselves to such a mechanism. For instance, consider a device such as is disclosed in U.S. Pat. No. 5,797,935, which issued to Barath for an invention entitled “Balloon Activated Forced Concentrators for Incising Stenotic Segments” and which is also assigned to the same assignee as the present invention. In such devices, the mechanism that advances the cutting elements (e.g. a balloon) does so by being reconfigured (i.e. inflated). Consequently, an independent protective device that does not accommodate such a reconfiguration and, instead, remains stationary would be inoperative for such a device purpose.
In light of the above, it is an object of the present invention to provide a protective sheath for a blade mounted on an inflatable balloon that is opened by balloon expansion to expose the blade. Another object of the present invention is to provide a protective sheath for a blade mounted on an inflatable balloon that protects the blade from inadvertently cutting tissue as the deflated balloon is maneuvered through the vasculature of a patent. Still another object of the present invention is to provide a protective sheath for a blade mounted on an inflatable balloon that is easy to use, relatively simple to manufacture and comparatively cost effective.